# positive second derivative

For instance, write something such as. IBM-Peru uses second derivatives to assess the relative success of various advertising campaigns. The concavity of a function at a point is given by its second derivative: A positive second derivative means the function is concave up, a negative second derivative means the function is concave down, and a second derivative of zero is inconclusive (the function could be concave up or concave down, or there could be an inflection point there). }\) This is because the curve $$y = s(t)$$ is concave up on these intervals, which corresponds to an increasing first derivative $$y =s'(t)\text{. d second derivative. }$$ Explain. }\), $$y = h(x)$$ such that $$h$$ is decreasing on $$-3 \lt x \lt 3\text{,}$$ concave up on $$-3 \lt x \lt -1\text{,}$$ neither concave up nor concave down on $$-1 \lt x \lt 1\text{,}$$ and concave down on $$1 \lt x \lt 3\text{. }$$ $$v$$ is decreasing from $$7000$$ ft/min to $$0$$ ft/min approximately on the $$54$$-second intervals $$(1.1,2)\text{,}$$ $$(4.1,5)\text{,}$$ $$(7.1,8)\text{,}$$ and $$(10.1,11)\text{. Put another (mathematical) way, the second derivative is positive. Likewise, on an interval where the graph of \(y=f(x)$$ is concave down, $$f'$$ is decreasing and $$f''$$ is negative. However, the existence of the above limit does not mean that the function ( Notice that we have to have the derivative strictly positive to conclude that the function is increasing. The middle graph clearly depicts a function decreasing at a constant rate. In (a) we saw that the acceleration is positive on $$(0,1)\cup(3,4)\text{;}$$ as acceleration is the second derivative of position, these are the intervals where the graph of $$y=s(t)$$ is concave up. }\) So of course, $$-100$$ is less than $$-2\text{. L v So: Find the derivative of a function; Then take the derivative of that; A derivative is often shown with a little tick mark: f'(x) The second derivative is shown with two tick marks like this: f''(x) Figure1.81The graph of \(y=v'(t)\text{,}$$ showing the acceleration of the car, in thousands of feet per minute per minute, after $$t$$ minutes. }\) We call this resulting function the second derivative of $$f\text{,}$$ and denote the second derivative by $$y = f''(x)\text{. 2 Graphically, the first derivative gives the slope of the graph at a point. x j x Take the derivative of the slope (the second derivative of the original function): The Derivative of 14 − 10t is −10 This means the slope is continually getting smaller (−10): traveling from left to right the slope starts out positive (the function rises), goes through zero (the … In particular, note that the following are equivalent: on an interval where the graph of \(y=f(x)$$ is concave up, $$f'$$ is increasing and $$f''$$ is positive. ( . $$F'(t)$$ has units measured in degrees Fahrenheit per minute. The car is stopped during the third minute. Overall, is the potato's temperature increasing at an increasing rate, increasing at a constant rate, or increasing at a decreasing rate? Recall that acceleration is given by the derivative of the velocity function. f''(x) = \lim_{h \to 0} \frac{f'(x+h)-f'(x)}{h}\text{.} = }\) Consequently, we will sometimes call $$f'$$ the first derivative of $$f\text{,}$$ rather than simply the derivative of $$f\text{.}$$. d Decreasing. On the interval $$-3 \lt x \lt 3\text{,}$$ how many times does the concavity of $$g$$ change? Try using $$g=F'$$ and $$a=30\text{. For example, the function pictured below in Figure1.84 is increasing on the entire interval \(-2 \lt x \lt 0\text{. The second derivative of a function f can be used to determine the concavity of the graph of f. A function whose second derivative is positive will be concave up (also referred to as convex), meaning that the tangent line will lie below the graph of the function. On which intervals is the velocity function \(y = v(t) = s'(t)$$ increasing? The graph of a function with a positive second derivative is upwardly concave, while the graph of a function with a negative second derivative curves in the opposite way. Whether making such a change to the notation is sufficiently helpful to be worth the trouble is still under debate. In terms of the potato's temperature, what is the meaning of the value of $$F''(30)$$ that you have computed in (b)? on an interval where $$a(t)$$ is zero, $$v(t)$$ is constant. x , − j x x For each of the values $$F'(30)$$ and $$F''(30)\text{,}$$ think about what they tell you about expected upcoming behavior in $$F(t)$$ and $$F'(t)\text{,}$$ respectively. ⁡ − sin This function is increasing at a decreasing rate. u d n Letting $$f$$ be a constant function shows that if the derivative can be zero, then the function need not be increasing. d For a certain function $$y = g(x)\text{,}$$ its derivative is given by the function pictured in Figure1.97. What are the units on $$s'\text{? Write several careful sentences that discuss (with appropriate units) the values of \(F(30)\text{,}$$ $$F'(30)\text{,}$$ and $$F''(30)\text{,}$$ and explain the overall behavior of the potato's temperature at this point in time. That is, At time $$t=0\text{,}$$ the car is at rest but gradually accelerates to a speed of about $$6000$$ ft/min as it drives about $$1300$$ feet during the first minute of travel. The scale of the grids on the given graphs is $$1\times1\text{;}$$ be sure to label the scale on each of the graphs you draw, even if it does not change from the original. The second derivative is defined by applying the limit definition of the derivative to the first derivative. on an interval where $$a$$ is positive, $$s$$ is . n \newcommand{\amp}{&} Decreasing? The graph of $$y=f(x)$$ is decreasing and concave down on the interval $$(3,6)\text{,}$$ which is connected to the fact that $$f''$$ is negative, and that $$f'$$ is negative and decreasing on the same interval. What are the units on $$s'\text{? The second derivative is negative (f00(x) < 0): When the second derivative is negative, the function f(x) is concave down. }$$ Then $$f$$ is concave up on $$(a,b)$$ if and only if $$f'$$ is increasing on $$(a,b)\text{;}$$ $$f$$ is concave down on $$(a,b)$$ if and only if $$f'$$ is decreasing on $$(a,b)\text{. … They tell us how the value of the derivative function is changing in response to changes in the input. Time \(t$$ is measured in minutes. Simply put, an increasing function is one that is rising as we move from left to right along the graph, and a decreasing function is one that falls as the value of the input increases. \end{equation*}, \begin{equation*} x On the graph of a function, the second derivative corresponds to the curvature or concavity of the graph. The formula for the best quadratic approximation to a function f around the point x = a is. The car's position function has units measured in thousands of feet. Look at the two tangent lines shown below in Figure1.77. 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